ANATOMY OF BIRDS. 



169 



ligible. Their bodies are oval, with the more powerful muscles 

 placed on the breast, so that, when the horizontal position is 

 assumed, the centre of gravity comes between the wings, and is 

 kept near the lower part by the weight of the pectoral muscles. 

 The length and flexibility of the neck enable the bird to make the 



Fig. 46.— Wing of Penguin. 



necessary changes in the centre of gravity, while the solidity of 

 the dorsal spine gives advantage to the action of the muscles. 

 The head is terminated by a pointed bill, which aids in cleaving 

 the air; the feet, when short, are drawn up and concealed under 

 the feathers ; when long, they are stretched out beneath or behind 

 the tail, which is more or less expanded, and helps to support 



Fig. 47 — Wing of Kamichi or Crested Screamer. 



the body in the air, as well as, by acting in the manner of a 

 rudder, to change its direction, or, by being expanded, to break 

 its descent." 



The wings of Birds (Figs. 45, 46, 47) are acute or obtuse. The 

 more angular the wing of birds — that is to say, the longer the feathers 

 on the edge of the wing — the more rapidly does it propel itself 

 through the air. The tail consists of a number of feathers, to which 

 are attached a series of small muscles, which are capable of depress- 



